It is, unfortunately, one of the risks of surgery in that area. However, over time, the tissue can become reinnervated and it may be a matter of being patient. You probably don't remember it, but it will have been detailed on the patient declaration of consent that you signed prior to the operation.
I have also been operated in that area, but managed to retain feeling. I suggest that you discuss it with your doctor. Perhaps, there are means of stimulating the area to encourage the nerves to reform? For example, massage, heat pads, sitz baths, to increase the blood flow in the tissue, to increase oxygenation and, hence, innervation. I am guessing here. Men have a higher risk of losing feeling and it can lead to impotence.
This is a medical matter and should be discussed with your doctors. I suggest that you make an appointment and inform the doctors what has happened. They should work with you to finding a solution, although they will most likely suggest that you wait several months to see whether the body heals itself (see above).
